Police officers, including Chief James Cetran, engaged in "active shooter" drills designed to train the department to respond to a mass shooting inside a school.

During a short break, training officer Sgt. Mike Connolly acknowledged that the exercise made him uncomfortable. But he said that after Dec. 14 shootings at Sandy Hook Elementary School in Newtown, in which 20 students and six educators were killed, the department needs to be ready.

"It's an unfortunate thing," Connolly said. "You have to be prepared. The reality is that people are doing these kinds of things."

Police took advantage of this week's school vacation to hold the exercise at Silas Deane Middle School.

Forty seven officers of all ranks, along with some Department of Corrections employees, practiced multiple scenarios for more than three hours Monday, Tuesday and Wednesday, Lt. Donald Crabtree said.

In addition to providing training, the drills familiarized officers with the school so they can navigate it quickly in an emergency, Crabtree said. School administrators also watched the drills, he said.

"The superintendent has been terrific to work with," Crabtree said. "I think it's been a good week with positive feedback from officers and school administrators who have seen what we're doing."

Superintendent Michael Emmett praised the department for its cooperation. He said he hoped that police would eventually conduct the exercises at all seven town schools to familiarize themselves with each layout.

For Wednesday's drills, officers used training weapons that fired paintball-like projectiles. Adding to the realism, a dispatcher radioed information to officers, and volunteers played students.

Responding officers came down the hallway in a tight pack, guns drawn, to confront a shooter carrying an AR-15 semiautomatic rifle, the same type of weapon used by killer Adam Lanza in Newtown.

When the exercise was over, Det. Anthony Demont critiqued the officers' performance, giving them mostly high marks. He reminded them to communicate constantly.

"The next time, we want to hear you guys talk to each other," Demont said. "Make sure it's loud: 'I'm covering that doorway.'"

The focus of the drill is simple: find the shooter and stop him, Connolly said.

"The whole purpose behind the active shooter [exercise] is you have to stop it from getting any bigger than it is," Connolly said. "If someone's hurting people, we want to stop it."